Dynamic Headspace Analysis Research Articles

Controlled volatile release from β-sitosterol-based oleogels based on different self-assembly mechanisms

This study examined how the self-assembly mechanisms of β-sitosterol-based oleogels influenced the release of volatile compounds. Microscopy, X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) measurements showed that the three β-sitosterol-based oleogels (β-sitosterol + γ-oryzanol oleogels (SO), β-sitosterol + lecithin oleogels (SL) and β-sitosterol + monostearate oleogels (SM)) had significant differences in their microstructures, which were formed via different self-assembly mechanisms. SO exhibited the highest oil binding capacity (OBC), complex modulus (G*) and apparent viscosity. Dynamic and static headspace analyses suggested that network structure of β-sitosterol-based oleogels affected the release of volatile components. SO showed the strongest retention effect, followed by SL and SM. The release of volatile compounds mainly related to structural strength and compositions of oleogels. These results indicated that β-sitosterol-based oleogels formed with different self-assembly mechanisms have the potential to serve as effective delivery systems for controlling the release of volatile compounds.

Release of Volatile Cyclopentanone Derivatives from Imidazolidin-4-One Profragrances in a Fabric Softener Application

Imidazolidin-4-ones were investigated as hydrolytically cleavable profragrances to increase the long-lastingness of perfume perception in a fabric softener application. The reaction of different amino acid amides with 2-alkyl- or 2-alkenylcyclopentanones as the model fragrances to be released afforded the corresponding bi- or tricyclic imidazolidin-4-ones as mixtures of diastereoisomers, which were separated by column chromatography. In polar solution, the different stereoisomers equilibrated under thermodynamic conditions to form mixtures with constant isomeric distributions, as shown by NMR spectroscopy. Dynamic headspace analysis on dry cotton demonstrated the controlled fragrance release from the precursors in practical application. Under non-equilibrium conditions (continuous evaporation of the fragrance) and depending on the structure and stereochemistry of the profragrances, the recorded headspace concentrations of the fragrance released from the precursors increased by a factor of 2 up to 100 with respect to the unmodified reference. Prolinamide-based precursors released the highest amount of fragrance and were thus found to be particularly suitable for prolonging the evaporation of cyclopentanone-derived fragrances on a dry cotton surface.

Synomones in necrophagous larvae of the blow flies Lucilia sericata and Calliphora vomitoria.

Chemical signals are widespread in insects, but those resulting in interspecific communication (i.e., synomones) remain understudied. Here, we analysed chemicals left on substrates by two species of blow fly larvae, Lucilia sericata (Meigen) and Calliphora vomitoria (Linneaus) (Diptera: Calliphoridae), which can aggregate together on carrion. Using solid-phase microextraction and dynamic headspace analysis, we identified six compounds common to both species: the decanoic, tetradecanoic, pentadecanoic, hexadecanoic and octadecanoic acids, and the 2-ethylhexyl salicylate. We then tested the behavioural effects of the decanoic and pentadecanoic acids using binary-choice experiments, along with the (Z)-9-tricosene, a pheromone found in many arthropods. The time spent by a larva and its average crawling speed were measured in two sides of an arena, where only one contained a compound at 0.25 or 25 μg/μl. No effect was observed when testing the decanoic acid. The pentadecanoic acid only reduced the speed of C.vomitoria larvae at 25 μg/μl. Finally, L.sericata larvae spent less time in the side containing the (Z)-9-tricosene at 0.25 μg/μl, whereas C.vomitoria spent more time and crawled faster in this side at 25 μg/μl. Although these results did not directly evidence synomones, they suggest that the (Z)-9-tricosene could regulate larval aggregations on carrion.

INVESTIGATION OF FLAVOUR PERMANENCE OF STRAWBERRY AND WATERMELON FLAVOURED CHEWING GUMS BY USING RETRONASAL AROMA TRAPPING DEVICE AND SENSORY ANALYSIS TECHNIQUES

Combining in vivo instrumental analysis with sensory evaluation techniques to analyze the release of volatile components from the gum matrix is gaining importance due to the flavour expectations of consumers. Besides consumers’ preferences and quality of flavourings determine the market value of chewing gums. In this study, strawberry and watermelon flavoured chewing gums were prepared and evaluated with both sensory evaluation and analytical techniques by using retronasal aroma trapping device and dynamic headspace analysis - DHA-GC/MS. Ethyl hexanoate and isoamyl acetate were chosen as flavour compounds for strawberry and watermelon flavoured gums to monitor in the study. The in vivo experiment with retronasal aroma trapping device showed that selected compounds were quite intense in the first 5 min of breath, and they were also detected in the 45th min of chewing. The flavour stability of the chewing gums was also monitored for 3 months. According to all sensory and instrumental analyzes, watermelon flavour was perceived as watermelon taste both at the 45th min and at the end of shelf life (equal to 12 months).

Optimization of gas sensors measurements by dynamic headspace analysis supported by simultaneous direct injection mass spectrometry

Dynamic headspace extraction is frequently used in gas sensors measurements. The procedure may introduce artefacts but its influence in sensor signals interpretation is rarely considered. In this paper, taking advantage of the on-line combination of a quartz microbalance gas sensor array with a proton transfer reaction mass spectrometer, we have been able to track the evolution of the concentration of volatile compounds along 75 s of extraction of the headspace of differently treated tomato pastes.Proton transfer reaction mass spectrometer signals show that VOCs are characterized by a large diversity of the evolution of the concentration. VOCs kinetics has been described by an electric equivalent circuit model.On the other hand, sensor signals continuously grow approaching a steady value. The contrasting behaviour between sensors signals and the concentration of most of VOCs is explained considering that water is the dominant component in the tomato paste sample and that water is one of those compounds whose concentration in the sensor cell steadily grows. Analysis of variance show that sensors signals achieve the largest separation between classes when the concentration of VOCs in the sensor cell reached its peak. Thus, although the sensor signals continue to rise their information content decays. This finding suggests that measurement protocols need to be adjusted according to the properties of the sample and that the actual measurement times could be much shorter than those predicted from the behaviour of sensor signal.

Design of Stimuli-Responsive Dynamic Covalent Delivery Systems for Volatile Compounds (Part 2): Fragrance-Releasing Cleavable Surfactants in Functional Perfumery Applications.

Amphiphilic imines prepared by condensation of a hydrophobic fragrance aldehyde with a hydrophilic amine derived from a poly(propylene oxide) and poly(ethylene oxide) diblock copolymer were investigated as cleavable surfactant profragrances in applications of functional perfumery. In water, the cleavable surfactants assemble into micelles that allow solubilization of perfume molecules that are not covalently attached to the surfactant. Dynamic headspace analysis on a glass surface showed that solubilized perfume molecules evaporated in a similar manner in the presence of the cleavable surfactant as compared with a non-cleavable reference surfactant. Under application conditions, the cleavable surfactant imine hydrolysed to release the covalently linked fragrance aldehyde. The profragrances were stable during storage in aqueous media, and upon dilution showed a blooming effect for the hydrolytical fragrance release and a more balanced performance of a solubilized perfume by retaining the more volatile fragrances and boosting the evaporation of the less volatile fragrances.

Biomass-derived carbon nanospheres decorated by manganese oxide nanosheets, intercalated into polypyrrole, as an inside-needle capillary adsorption trap sorbent for the analysis of linear alkylbenzenes

Carbon nanospheres (CNSs) were derived hydrothermally from biomass (orange peels) and decorated by manganese dioxide (MnO2) nanosheets. The MnO2/CNSs nanocomposite was intercalated into polypyrrole (PPy) during flow-through in-situ electropolymerization of pyrrole on the surface of the inner wall of a stainless-steel needle to prepare an inside-needle capillary adsorption trap (INCAT) device. The surface morphology, thermogravimetric behavior, sorption characteristics, and structure of the MnO2/CNSs@PPy nanocomposite were characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX), nitrogen physisorption by the Brunauer-Emmett-Teller (BET) method, dynamic light scattering (DLS) size distribution, and Fourier-transform infrared spectrometry (FT-IR). The INCAT device was coupled with GC-FID and applied for dynamic headspace analysis of linear alkyl benzenes (LABs) in wastewater samples. The effective experimental variables on the extraction efficiency was optimized using a central composite design (CCD) based on response surface methodology (RSM). Under the optimal conditions, the limits of detection (LODs) were in the range of 0.5–1.0 ng mL−1. The calibration plots were linear over the range of 0.01–10 μg mL−1. The relative standard deviations (RSDs%) for intra-day, inter-day, and inter-INCAT precision were calculated 5.3–8.3%, 9.4–13.5%, and 13.6–16.9%, respectively. The developed technique was employed successfully for the analysis of LABs in water and wastewater samples with average recovery values ranging from 92 to 109%. A single INCAT device was used more than 90 times without significant change in its extraction capability.

Polystyrene‐Based 2‐Oxoacetates for the Light‐Induced Release of Fragrances Under Realistic Application Conditions

AbstractLight‐sensitive 2‐oxoacetate‐derived polystyrene copolymers are investigated for the controlled release of fragrances. The stimuli‐responsive delivery systems are efficiently prepared in a two‐step reaction sequence. Simultaneous Friedel–Crafts acylation and cationic polymerization of styrene give access to 2‐oxoacetate‐derived polystyrenes in one step; the fragrance to be released is then introduced by organotin‐catalyzed transesterification in a second step. The performance of the copolymer conjugates releasing either individual fragrance raw materials or a fragrance mixture is evaluated by dynamic headspace analysis in the presence of surfactants on different substrates and compared with their non‐polymeric analogues. Direct and indirect deposition of the delivery systems onto cotton in a fabric softening application show that differences in performance are correlated with the amount of surface deposition. In the present study, the copolymer that releases a fragrance mixture performs better than the copolymers that release the corresponding fragrances individually and better than the respective non‐polymeric profragrances.

Hydrogel particles as a controlled release delivery system for lavender essential oil using pH triggers

Owing to the antibacterial properties of lavender essential oil (LEO), it can be used in food packaging to improve food quality and increase shelf life. LEO has also been shown to be effective for the treatment of several neurological disorders, including depression and insomnia. However, the practical applicability of LEO is limited by its high volatility. This study aimed to investigate the possibility of using hydrogel particles as carriers to encapsulate and control the release of LEO, thereby improving its storage and delivery. LEO was first loaded into oil-in-water emulsions that were then encapsulated in hydrogel particles. These hydrogel microparticles were cross-linked with different concentrations of Ca2+. The influence of Ca2+-mediated cross-linking on the properties and stability of the hydrogel microparticles was investigated. The release of LEO from the hydrogels was determined by dynamic and static headspace analyses. The results showed that the hydrogel particles not only improved LEO stability during storage but also delayed LEO release under real-time, dynamic conditions. This study suggests the potential application of hydrogels as a novel aroma delivery system for the controlled release of essential oils.

반응표면분석법을 이용한 Trimethylamine의 Static과 Dynamic Headspace 분석 방법 최적화

반응표면분석법을 이용한 Trimethylamine의 Static과 Dynamic Headspace 분석 방법 최적화

Dynamic headspace analysis using online measurements: Modeling of average and initial concentration

Dynamic headspace sampling is an important technique for the analysis of consumer products, the study of biological samples and environmental water analyses. This paper shows the influence of experimental conditions, such as the sampling time, sampling flow rate, headspace volume, liquid volume and Henry coefficient on the measured average concentration values. A corresponding closed expression as function of these variables is introduced in order to quantify the deviation of the initial headspace concentration. The proposed bi-exponential function embeds different current existing models for recovery calculation in dynamic sampling analyses in one single expression. A fully automated and user-friendly Excel® file to investigate or to model the dynamic headspace sampling results is added to everyone's easy use.

Developing Multi Stimuli‐Responsive Core/Shell Microcapsules to Control the Release of Volatile Compounds

AbstractEncapsulation of 2‐oxoacetates into poly(urea‐urethane) core/shell microcapsules allows the light‐induced controlled release of volatile compounds such as fragrances, plant volatiles, pheromones, or other semiochemicals. On exposure to UVA light, 2‐oxoacetates decompose to form a carbonyl compound together with CO2or CO, which can build overpressure inside the capsules that expands and/or cleaves the capsule wall to release its content. The influence of the structure and ratio of the polyisocyanates and diamines used for interfacial polymerization, as well as the composition of the capsule wall and the oil phase, are investigated by dynamic headspace analysis of the released volatile compounds to optimize the performance of the delivery system. The combination of a light‐induced release with the mechanical cleavage of the capsule gives access to multi stimuli‐responsive systems that selectively respond to the different triggers applied. Furthermore, the concept outlined in the present work is generally applicable to other photolabile precursors that generate a gas inside the capsules and thus release co‐encapsulated active molecules as a direct response to light.

Determination of cannabinoid vapor pressures to aid in vapor phase detection of intoxication

The quest for a reliable means to detect cannabis intoxication with a breathalyzer is ongoing. To design such a device, it is important to understand the fundamental thermodynamics of the compounds of interest. The vapor pressures of two important cannabinoids, cannabidiol (CBD) and Δ9-tetrahydrocannabinol (Δ9-THC), are presented, as well as the predicted normal boiling temperature (NBT) and the predicted critical constants (these predictions are dependent on the vapor pressure data). The critical constants are typically necessary to develop an equation of state (EOS). EOS-based models can provide estimations of thermophysical properties for compounds to aid in designing processes and devices. An ultra-sensitive, quantitative, trace dynamic headspace analysis sampling called porous layered open tubular-cryoadsorption (PLOT-cryo) was used to measure vapor pressures of these compounds. PLOT-cryo affords short experiment durations compared to more traditional techniques for vapor pressure determination (minutes versus days). Additionally, PLOT-cryo has the inherent ability to stabilize labile solutes because collection is done at reduced temperature. The measured vapor pressures are approximately 2 orders of magnitude lower than those measured for n-eicosane, which has a similar molecular mass. Thus, the difference in polarity of these molecules must be impacting the vapor pressure dramatically. The vapor pressure measurements are presented in the form of Clausius-Clapeyron (or van’t Hoff) equation plots. The predicted vapor pressures that would be expected at near ambient conditions (25°C) are also presented.

Floral scent chemistry and pollination in the Neotropical aroid genus Xanthosoma (Araceae)

The Neotropical aroid genus Xanthosoma (Caladieae, Araceae) embraces about 140 species of tuberous herbs whose night-blooming inflorescences emit strong, pleasant floral scents, presumably involved in the atttaction of pollinators. The number of studies on the floral scent chemistry of aroids, as well as on their role in pollinator attraction, has undergone a considerable increase in the last decade. In Xanthosoma, however, neither have never been properly assessed. In the present study, we provide an overview on the reproductive and pollination biology of Xanthosoma species and add new reports on the pollinators of some species. Furthermore, we investigate the floral scent chemistry of 13 species through dynamic headspace sample collection and analysis by gas chromatography coupled to mass spectrometry (GC–MS). A thorough literature survey and novel data from our own personal findings revealed that floral visitors are known for only 12 species of Xanthosoma, which represent less than 10% of its currently documented species diversity. Cyclocephaline scarabs (Melolonthidae, Cyclocephalini) were reported in inflorescences of 11 of the 12 species and are assumed to be the main pollinators associated with them. A total of 76 VOCs, mainly terpenes and benzenoids, were detected. Floral scent bouquets diverge considerably among analyzed species of Xanthosoma mainly due to the presence of unique prominent compounds that ensure originality of the blends rather than because of their quantitative complexity (number of constituents), as analyzed samples were typically dominated by few (2–4) VOCs that together accounted for >80% of the total relative scent discharge. A number of these dominant VOCs had already been isolated in other species of aroids and reported as effective attractants of cyclocephaline scarabs in field biossays, namely (Z)-jasmone, p-vinylanisole and dihydro-β-ionone and we speculate that along with other dominant compounds they are directly involved in pollinator selection in Xanthosoma.

Photolabile acetals as profragrances: the effect of structural modifications on the light-induced release of volatile aldehydes on cotton.

Because volatile compounds evaporate from surfaces that are usually exposed to daylight, photoresponsive delivery systems are particularly suitable to control their release. In the present study, we investigated 4,4-diphenyl-4H-benzo[d][1,3]dioxins as profragrances for the light-induced delivery of aldehydes in functional perfumery. The efficiency of fragrance release was investigated on cotton after direct and indirect surface deposition from a fabric softening formulation as a function of the substitution pattern of the profragrance structure. Dynamic headspace analysis above the cotton surface demonstrated that the structure of the profragrance had a much larger effect on the fragrance release than did the amount of deposition on the target surface. Although some trends observed for the photolysis in solution also applied to the reaction on cotton, it is not generally possible to predict the photochemical behaviour of structurally different precursors on surfaces from their solution properties. The fact that the present system performed on a dry surface makes it an interesting light-triggered delivery vehicle for other classes of bioactive volatile compounds, such as pheromones or agrochemicals.

Static and dynamic headspace analysis of instant coffee blends by proton-transfer-reaction mass spectrometry.

Instant coffee is a widespread product, generally related to a high consumer acceptability, also because of its ease of preparation. The present work addresses the characterization of the headspace of freshly brewed instant coffees resulting from different blends, during and immediately after preparation. The sample set consisted of 10 coffees, obtained by mixing three different blends in different proportions. The employment of Proton Transfer Reaction-Mass Spectrometry (PTR-MS) allowed for direct and real-time sampling from the headspace, under conditions that mimic those that are encountered above the cup during and right after brewing. Different coffee brews were separated on the basis of the respective volatile profiles, and data showed good consistency with the respective blend compositions. When the headspace evolution was monitored during preparation, similar results were obtained in terms of blend separation; moreover, different blends displayed different and reproducible 'signatures' in terms of time evolution. A straightforward method for the prediction of headspace composition is proposed, allowing to predict the volatile profiles of two-component and three-component blends on the basis of the respective parent components. Overall, the results constitute a successful example of the applicability of PTR-MS as a tool for product development in food science. Copyright © 2015 John Wiley & Sons, Ltd.

Olive oil phenolic compounds affect the release of aroma compounds

Twelve aroma compounds were monitored and quantified by dynamic headspace analysis after their addition in refined olive oil model systems with extra virgin olive oil (EVOO) biophenols to simulate EVOO aroma. The influence of polyphenols on aroma release was studied under simulated mouth conditions by using human saliva, and SPME–GC/MS analysis. While few differences were observed in orthonasal assay (without saliva), interesting results were obtained for retronasal aroma. Biophenols caused generally the lowest headspace release of almost all volatile compounds. However, only ethyl esters and linalool concentrations were significantly lower in retronasal than orthonasal assay. Saliva also caused higher concentration of hexanal, probably due to hydroperoxide lyase (HPL) action on linoleyl hydroperoxides. Epicatechin was compared to EVOO phenolics and the behaviour was dramatically different, likely to be due to salivary protein–tannin binding interactions, which influenced aroma headspace release. These results were also confirmed using two extra virgin olive oils.

Optimum temperature for floral terpene emissions tracks the mean temperature of the flowering season.

Emissions of volatiles from leaves exhibit temperature dependence on maximums, but the optimum temperatures for the release of floral volatiles and the mechanism(s) of optimising these emissions have not been determined. We hypothesised that flowers have an optimum temperature for the emission of volatiles and, because the period of flowering varies highly among species, that this optimum is adapted to the temperatures prevailing during flowering. To test these hypotheses, we characterised the temperature responses of floral terpene emissions of diverse widespread Mediterranean plant species flowering in different seasons by using dynamic headspace sampling and analysis with GC-MS. The floral emissions of terpenes across species exhibited maximums at the temperatures corresponding to the season of flowering, with the lowest optimal temperatures observed in winter-flowering and the highest in summer-flowering species. These trends were valid for emissions of both total terpenes and the various terpene compounds. The results show that the optimum temperature of floral volatile emissions scales with temperature at flowering, and suggest that this scaling is the outcome of physiological adaptations of the biosynthetic or emission mechanisms of flowers.

Thioether profragrances: parameters influencing the performance of precursor-based fragrance delivery in functional perfumery.

A series of thioether profragrances was prepared by reaction of different sulfanylalkanoates with δ-damascone and tested for their release efficiencies in a fabric-softener and an all-purpose cleaner application. Dynamic headspace analysis on dry cotton and on a ceramic plate revealed that the performance of the different precursors depended on the structure, but also on the particular conditions encountered in different applications. Moreover, profragrances derived from other α,β-unsaturated fragrance aldehydes and ketones were synthesized analogously and evaluated using the same test protocol. Thioethers were found to be suitable precursors to release the corresponding fragrances, but neither the quantity of profragrance deposited from an aqueous environment onto the target surface, nor the amount of fragrance released after deposition could be linearly correlated to the hydrophilicity or hydrophobicity of the compounds. Different sets of compounds were found to be the best performers for different types of applications. Only one of the compounds evaluated in the present work, namely the thiolactic acid derivative of δ-damascone, efficiently released the corresponding fragrance in both of the tested applications. Profragrance development for functional perfumery thus remains a partially empirical endeavour. More knowledge (and control) of the various application conditions are required for an efficient profragrance design.

Sorbent-packed needle microextraction trap for synthetic musks determination in wastewater samples

A needle trap (NT) device filled with HF Bondesil-C18 as a sorbent material was evaluated for the dynamic headspace analysis of a family of nine synthetic musks compounds that include two nitro musks, six polycyclic musks (with galaxolide and tonalide as the most widespread used polycyclic musks) and the degradation product of galaxolide (galaxolidone) in wastewater samples. Different parameters affecting the adsorption capacity of the sorbent were studied (e.g. extraction mode, extraction temperature, salt concentration, preincubation time fill and ejection speed or fill volume). Furthermore, injection parameters used with the NT device (e.g. desorption mode, desorption temperature and time) were evaluated to optimize the desorption and transfer of the target compounds into the GC column. Method detection limits obtained with gas chromatography–tandem mass spectrometry (GC–MS/MS) detection were found in the low ngL−1 range, between 2.5 and 10ngL−1, depending on the target compounds. Moreover, under optimized conditions, the method gave good levels of intra-day and inter-day repeatabilities in wastewater samples with relative standard deviations (n=5, 100ngL−1) less than 11 and 17%, respectively. The developed method was satisfactorily applied to the analysis of aqueous samples obtained from three wastewater treatment plants. All the polycyclic musks studied were detected in influent samples with cashmeran, galaxolide and tonalide as the most representative compounds. The analysis of effluent wastewater showed a decrease in the concentrations of all of the polycyclic musk detected in influent samples and an increase in the concentration of galaxolidone until a maximum value of 820ngL−1.